The present invention relates to a method for detecting cancer on skin of humans and mammals by imaging spectroscopy. Spectroscopy can be performed in that a chemical agent is collected on or in the cancer cells which agent makes a fluorescent irradiation having a certain wave-length when it is illuminated with normal light or a certain wave-length. The invention also includes an arrangement for performing the method.
It is well known that cancer can have many different shapes both within the body and on the skin. Also skin cancer can be divided in different categories such as basiloma, squamous cell carcinoma and malignant melanoma. From these mentioned kinds the latter is the most serious one, whereas the first mentioned is the least serious one and results in complications only when this type of cancer is located on special sensible parts of the body, such as on the eyelid, the nose or the like.
When for example basiloma cancer is developed, the surgeon will simply cut away the sick part and a piece outside this so that he will be sure that all has been cut away. On some places such as on an eyelid it is not possible to cut away too much and the surgeon then will first cut away that area in which he with certainty can see is attacked whereafter he will cut away strips of the surrounding skin area and these strips will be microscopically investigated to control that the whole attacked area has been taken away. It may become necessary to cut out many strips and such an operation can take many hours in that the investigation of the strips takes its time. This operation method is called Moh""s surgery.
When a cancer tumour or a cancer stain has developed, so that it is visible, no detection method is needed to find it. However, it is of vital importance that cancer in a development stadium which cannot be seen with the eye also can be detected so that early measures can be applied. For this purpose it is known to use for example spectroscopy which means that the area where cancer can be suspected to be present is illuminated and fluorescent light which is irradiated from the illuminated area and which comes from the agents which has been collected in or around the cancer cells are detected. Such an agent can be a derivative of haematoporphyrin which consists of different porphyrines and which is injected in the blood. After injection of this agent the illumination is delayed until the haematoporphyrin derivative has disappeared from the healthy tissues which does not occur in cancer attacked tissues where these derivatives instead are collected. The illumination occurs preferably with laser light. Besides that it is possible to detect the cancer cells by the irradiated fluorescent light the cancer is also treated by applying such a strong light that oxygen in status nascendi is formed so that the cells are killed. This method and the production of haematoporphyrin is described in the U.S. Pat. No. 5,015,463. A similar method and an apparatus for detection is described in the Swedish patent 84 05 276-0.
It is also possible to detect sickly changes in the body without the use of any chemical agent and only by means of a mapping of the irradiated fluorescent light which is created by means of a light source. When light containing different wave-lengths is applied an auto-fluorescence is namely created from healthy tissue in the body and this can then be mapped. At sick areas the fluorescent picture is changed and the sick area can therefore be located. The light source at such an investigation is preferably laser light. The system and apparatus are disclosed in the American patent U.S. Pat. No. 5,345,941.
A method for detection of cancer is described in WO 93/13403. Here delta aminolevulinic acid is applied to the skin and the ratio between the specific peak of fluorescence intensity in red and in blue-green is used for the detection when the excitation is made the ultra violet, violet, or blue wave range.
The Technical Problem
With the first method of Moh""s surgery the apparent disadvantage of the treatment is that it takes very long time and creates suffering for the patient and is also costly. This operation is therefore performed only at very few areas.
With the second method when haematoporphyrin is injected the problem is that the heamatoporphyrin derivative is not an agent of the some persons and that also a long time has to lapse before this agent has disappeared from the healthy tissues before the examination can be started.
The third method with mapping the auto fluorescence without help of any contrasting agent, color or the like is complicated and not reliable and requires also a very expensive equipment.
The Solution
It has therefore for long been a desire to be able to discover skin cancer at a very early stage in a reliable way without injecting substances not belonging to the body in a quick way and with a speedy and inexpensive apparatus and according to the invention one has therefore brought about a method for detecting cancer on skin of humans and mammals by imaging spectroscopy which is characterized in that a composition containing delta amino levulinic acid (ALA) first is applied on that area of the skin where cancer is suspected to be present and is allowed to stay there for 1 to 24 hours whereupon the skin area which has been influenced with ALA after removing the composition is illuminated with light having a wave-length of 363-367 nm and 404-408 nm and an intensity of 0,1-10 mW/cm2 and that during the illumination arising fluorescent irradiation having a wave-length of 610-715 nm from the area which is radiated with light is registered and evaluated.
It is according to the invention suitable that the registration of the fluorescent irradiation occurs by photographing with a camera preferably of the type CCS (Charge Coupled Device) on which a filter which is blocking all light having a wave-length shorter than 610 nm is applied.
According to the invention it is suitable that the composition consists of ALA in concentration of 5-25% in an oil-in-water or water-in-oil, emulsion.
The illumination with light is according to the invention created by a mercury lamp which after filtering (with filter BG12) gives light within the described area.
The invention includes also use of an apparatus for performing the method and comprises a source of light in the form of a mercury lamp for creating, normal noncoherent light, a filter (BG12) for filtering of the light created by the light source which filter allows light with a wave-length of 363-367 nm and 404-408 to penetration, a registration device for registering of fluorescent light having a wave-length of 610-715 nm from the skin area which has been illuminated with the created and filtered light and a composition containing delta amino levulinic acid for application on the skin area which is intended to be examined.
The registering equipment according to the invention consists suitably of a camera preferably of the type CCD (Charge Coupled Device) on which a filter which blocks all light having a wave-length lower than 610 nm has been applied.
The composition according to the invention consists suitably of an oil-in-water or a water-in-oil emulsion containing 5-12% ALA.